A mobile terminal device used in a mobile communication system, e.g., a mobile phone, may be provided with a switch circuit (a radio frequency switch circuit) that performs switching of radio frequency signals. Such a radio frequency switch circuit may adopt a multistage-coupling configuration in which switching elements such as GaAs-based FETs (Field Effect Transistors) may be coupled in series. This allows for suppression of signal distortion upon input of a radio frequency signal of large electric power (large amplitude), leading to an increase in maximum electric power to be handled.
In the multistage-coupling configuration, simply increasing the number of stages of FETs may lead to inconvenience such as greater insertion loss because of an increase in ON resistance of the FETs. One of known methods of enhancing the maximum electric power to be handled, without a significant increase in the number of stages of the FETS, is a technique of inserting an additional capacitor between a gate electrode and a drain electrode, or between the gate electrode and a source electrode, of the FET. For example, Patent Literature 1 proposes forming an additional-capacitor strip projected from a bend of a gate electrode of a meandering shape, to form an additional capacitor Cadd/2 between the additional-capacitor strip and the a drain electrode (or a source electrode).